Thin film resistors are well known and may comprise a variety of resistive materials, with the resistive materials such as nickel chromium, silicon chromium and tantalum silicon nitride being common. These types of thin-film resistors are formed in the back end of line (BEOL) of an integrated circuit manufacturing flow. In contrast to resistors located in the silicon substrate which suffer from relatively large parasitic capacitance to the substrate, back end resistors have much less parasitic capacitance, since they are placed vertically above the substrate. Hence, BEOL resistors are preferred for high frequency RF applications.
Integrating a thin film resistor in the BEOL of an integrated circuit manufacturing flow adds cost and cycle time. A typical process flow for integrating a thin film resistor into an integrated circuit manufacturing may add two to three additional masking steps. To achieve high values of resistance, very thin films on the order of 1 to 10 nm may be required. One masking and etching step may be used to define the resistor. Since the resistor material is so thin, a special resistor contact pattern and etch may be required to form good electrical contact without damage to the thin resistor material, undesirably adding to fabrication cost and complexity. An alternative method may be to deposit a conductive landing pad material over the thin film resistor and then pattern and etch the material to provide landing pads for the contact etch. Etching the conductive landing pad material may damage the thin film resistor.